NASA Daily News Summary
For Release: Oct. 5, 1999
Media Advisory m99-205
Summary:
SPACECRAFT PROVIDES FIRST DIRECT EVIDENCE: SMOKE IN THE
ATMOSPHERE INHIBITS RAINFALL
Video File for Oct. 5, 1999
ITEM 1 - RAIN SLOWS AS FIRES FLARE--BIOMASS BURNING AND THE
WEATHER (TRMM SATELLITE)
ITEM 2 - MARS METEORITE OR MARS ROCK? (replay)
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SPACECRAFT PROVIDES FIRST DIRECT EVIDENCE:
SMOKE IN THE ATMOSPHERE INHIBITS RAINFALL
For the first time, researchers have proven that smoke from
forest fires inhibits rainfall. The findings, to be published in
the Oct. 15 issue of Geophysical Research Letters, are based on an
extensive analysis of data taken from NASA's Tropical Rainfall
Measuring Mission (TRMM) spacecraft.
The study shows that the "warm rain" processes that often
create rain in tropical clouds are practically shut off when the
clouds are polluted with heavy smoke from forest fires. In these
clouds, scientists found, the cloud tops must grow considerably
above the freezing level (16,000 feet) in order for them to start
producing rain by an alternative mechanism.
Contact at NASA Headquarters, Washington, DC: David E. Steitz
202/358-1730.
Contact at NASA Goddard Space Flight Center, Greenbelt, MD: Allen
Kenitzer 301/286-2806.
Contact at American Geophysical Union, Washington, DC: Harvey
Leifert 202/777-7507.
For full text, see:
ftp://ftp.hq.nasa.gov/pub/pao/pressrel/1999/99-110.txt
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If NASA issues additional news releases later today, we will e-
mail summaries and Internet URLs to this list.
Index of 1999 NASA News Releases:
http://www.nasa.gov/releases/1999/index.html
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ITEM 1 - RAIN SLOWS AS FIRES FLARE--BIOMASS BURNING TRT 6:24
AND THE WEATHER (TRMM SATELLITE)
Using data collected from the Tropical Rainfall Measuring Mission
(TRMM) satellite, scientists now have conclusive proof that forest
fire smoke inhibits rainfall. Research conducted over parts of
Indonesia during some of that countryıs most severe forest fires
showed strong signs of rainfall inhibition in areas that were
blanketed with smoke. Areas comparatively free of smoke particles
produced rain normally.
This research is vital in understanding how global precipitation
affects the weather; tropical rainfall accounts for nearly two
thirds of energy necessary to power atmospheric circulation. This
study helps researchers quantify the phenomena, helping to better
assess human impacts on the weather, both for discrete regions of
the planet as well as globally.
Contact at NASA Headquarters, Washington, DC: David E. Steitz
202/358-1730.
Contact at NASA Goddard Space Flight Center, Greenbelt, MD: Allen
Kenitzer 301/286-2806.
ITEM 1a - HOW SMOKE INHIBITS RAINFALL: NORMAL CONDITIONS TRT :10
Under normal conditions, tropical clouds swell with water
droplets. Those droplets have a tendency to clump together, thus
increasing their weight relative to the surrounding cloud. As
they coalesce, they fall out of the cloud as rain.
ITEM 1b - HOW SMOKE INHIBITS RAINFALL: SMOKY CONDITIONS TRT :08
In areas of concentrated biomass burning, water condenses around
tiny particles of smoke, called nuclei. These nucleated drops
tend not to clump together, remaining trapped in the clouds,
inhibiting rainfall. From space, heavily nucleated clouds appear
brighter due to the fact that there are more free floating,
smaller water particles available to reflect and scatter light.
ITEM 1c - HOW SMOKE INHIBITS RAINFALL: COMPARISON OF TRT :18
CONDITIONS
In this animation, compare the two systems side by side. You can
see how the rain-producing cloud on the left is composed of larger
water droplets, making it easier for them to coalesce and fall out
as precipitation. On the right, notice how the smaller, nucleated
particles tend to remain apart, without forming larger drops. This
smoke-affected cloud will not produce rain.
ITEM 1d - INHIBITED RAIN IN BORNEO: SATELLITE DATA CONFIRMS
OBSERVATIONS
The Indonesian island of Borneo falls directly in the
observational path of the research instruments. By measuring the
amount of smoke and other aerosols above a given region, and
matching that data with measurements regarding specific amounts of
rainfall, researchers have concluded a distinct cause and effect
relationship between aerosols and rainfall.
ITEM 1e - SATELLITE DATA DISSOLVE SEQUENCE TRT 1:08
Readings from the TOMS (Total Ozone Mapping Spectrometer)
satellite measured aerosol levels above Borneo throughout February
1998. Immediately following, a sequence of color-coded images
appears over the Borneo map. Red represents fires and hot spots.
Clouds and smoke appear next, overlaid on the entire image. Note
the heavy stripes of smoke toward the right and upper right of the
image. Light blue notes concentrations of water droplets, while
dark blue marks areas with precipitation. Notice how there are no
indications of rain near the island hot spots and smoky regions.
Finally, we show the map as a composite image of the various data
sets.
ITEM 1f - TRMM SATELLITE ANIMATION TRT :24
The TRMM (Tropical Rainfall Measuring Mission) satellite measures
tropical rainfall in a band around the Earth stretching 35 degrees
north and south of the equator. The instrument uses several
instruments to detect rainfall, including radar, microwave
imaging, and lightning sensors. TRMM data is available to
researchers around the world; it is managed by a team at NASAıs
Goddard Space Flight Center in Greenbelt, MD.
ITEM 1g - INTERVIEW/SOUNDBITES TRT 1:37
Dr. Christian Kummerow, TRMM Project Scientist
ITEM 2 - MARS METEORITE OR MARS ROCK? (replay) TRT 3:47
Martian meteorite carbonates--3.9 billion years old.
A new study of the carbonite minerals found in a meteorite from
Mars shows they were formed about 3.9 billion years ago.
Scientists believe the planet had flowing surface water and warmer
temperatures then, making it more Earth-like. The carbonates
themselves are tiny deposits--reddish globules, some with purplish
centers and many surrounded by white borders. Researchers at
NASA's Johnson Space Center in Houston, TX, and the University of
Texas at Austin did the study using different techniques.
Contact at NASA Johnson Space Center, Houston, TX: John Ira Petty
281/483-5111.
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